This invention relates to disassembling tube type heat exchangers and more particularly to an extractor for pulling individual tubes from a tube sheet in heat exchangers, boilers, and the like.
Many heat exchangers are of an indirect type which employ tubes for carrying a heat transfer fluid. A large number of the tubes are mounted to extend in a parallel grid between two supporting tube sheets in such heat exchangers. The tubes are pressed into or expanded into engagement with openings through the tube sheet for forming a fluid tight seal. A heat transfer fluid, such as water, is circulated through the parallel tubes between the two tube sheets while a different temperature fluid, such as combustion gases or heated water is circulated past the exterior of the tubes between the two tube sheets for achieving indirect heat transfer between the two fluids. It is sometimes necessary to remove tubes from the tube sheets in which they are mounted. This may be necessary for many reasons, such as leaks in the tubes or excessive scale accumulations within the tubes.
The tubes commonly are held in the tube sheets by expanding the ends into engagement with the internal walls of openings through the tube sheets and are securely held therein by hoop stresses created by the expanding process. Various methods are used for relieving these hoop stresses to remove tubes from the tube sheets. One method used for removing the hoop stresses holding the tubes within the tube sheets is by cutting axial slots within the expanded end portion of the tube passing through the tube sheet, as disclosed in U.S. Pat. No. 3,628,246 which issued Dec. 21, 1971. Another method used for relieving tube stresses involves engaging the interior walls of the tube with expandable jaws on a mandrel and, subsequently, retracting a hydraulic cylinder connected to the mandrel to pull the tube end from the tube sheet, as disclosed in U.S. Pat. No. 3,835,520 which issued Sept. 17, 1974. After the hoop stresses are removed, it is necessary to pull the entire length of the tube through the tube sheet. This may be a difficult and time consuming process since tubes in some indirect heat exchangers, such as those used in nuclear reactors, may be on the order of 30 to 70 feet long and of considerable weight.